Apparatus with saw-toothed blade for cutting tissue

ABSTRACT

A tissue splitting device for splitting a harvested soft tissue to provide a layer of tissue having a uniform thickness and methods for tissue transplantation using uniform layers of tissue.

BACKGROUND OF THE INVENTION Field of Invention

The present invention relates to the field of reconstructive surgery andparticularly to a tissue splitting device that produces viable,undamaged and uniformly sized soft tissue layers for transplantation.

Description of Related Art

Soft tissue grafts are commonly used in reconstructive surgery includingfor gingival, dermal, and cartilage grafting and sometimes for bonegrafting. Traditionally a surgeon manually trims a harvested tissue toprepare a graft having a desired size and thickness for implantation ata grafting site; Rijhwani et al., Free Gingival Autograft andSubepithelial Connective Tissue Graft for the Treatment of GingivalRecession: A Brief Review and Report of Three Cases. Seema Yadav Journalof Contemporary Dentistry, September-December 2016; 6(3):225-232; HarrisR J. Creeping attachment associated with the connective tissue withpartial-thickness double pedicle graft. J. Periodontol. 1997 September;68(9):890-9.

Soft tissue grafts include gingival grafts which are commonly madewithin the oral cavity. Such grafts include free gingival grafts,connective tissue grafts, and pedicle grafts. An oral graft is often astrip of tissue which is obtained most commonly from an intraoral donorsite such as the hard palate.

Such grafts are often necessary to treat gum recession, cover theexposed root, increase tissue thickness to provide or enhancekeratinized tissue, or to treat gum or tooth sensitivity; Rijhwani etal, 2016, supra. Gum recession occurs when the teeth roots becomeexposed. There are several reasons for gum recession which include gumdisease, trauma, aging, over brushing, and poor tooth position;Dembowska E, et al., Subepithelial connective tissue graft in thetreatment of multiple gingival recession. Oral Surg Oral Med Oral PatholOral Radiol Endod. 2007 September; 104(3):e1-7. Epub 2007 July 6;Rijhwani et al, 2016, supra; Wang L, et al., Refinement and Evaluationof Modified Minimally Invasive Harvest Technique for SubepithelialConnective Tissue. J Craniofac Surg. 2018 July; 29(5):1287-1290. Gumrecession and tooth exposure often result in a patient havinguncomfortable sensations when eating hot, cold foods, or when the teethare exposed to air. Gum recession is also associated with a higher riskof caries and with an unaesthetic appearance and often leads to adiminished self-image.

Besides oral grafts, soft-tissue grafts have been used to reconstructthe anterior cruciate ligament with hamstring or fascia lata (deepfascia of the thigh) grafts within the femoral tunnel in the knee jointwhich is a common area of tearing of these ligaments in sportsactivities such as football or skiing; Wilde J, et al., Revisionanterior cruciate ligament reconstruction. Sports Health. 2014 November;6(6):504-18.

There are several ways to obtain a tissue graft. Tissue, such asconnective tissue from the palate, to be used as a connective tissuegraft may be harvested using the trap-door technique described by Edel,A. Clinical evaluation of free connective tissue grafts used to increasethe width of keratinized gingiva. J Clin Periodontol 1974; 1:185-96.Another method is the parallel incision method developed and describedby Langer B and Langer L. Subepithelial connective tissue grafttechnique for root coverage. J. Periodontol. 1985; 56:715-20. Othermethods include those modified by Harris who provided a new method usinga scalpel with two blades mounted 1.5 mm apart; Harris R. J., Theconnective tissue and partial thickness double pedicle graft: Apredictable method of obtaining root coverage. J. Periodontol. 1992;63:477-86; by Raetzke who introduced the two crescent-shaped horizontalincisions to obtain graft; tissue; Raetzke P B. Covering localized areasof root exposure employing the “Envelope” technique. J. Periodontol.1985; 56:397-402; by Bruno used the two horizontal incisions only; BrunoJ F. Connective tissue graft technique assuring wide coverage. Int. J.Periodontics Restorative Dent. 1994; 14:127-37; and by Hurzeler who useda single incision technique which has several advantages such as theprimary healing at the donor site and very slight postoperative pain andcomplications; Hurzeler M B, Weng D. A single incision technique toharvest subepithelial connective tissue grafts from palate. Int JPeriodontics Restorative Dent. 1999; 19:279-87—each incorporated hereinby reference in its entirety.

Typically palatial connective tissue is harvested using a blade orientedperpendicular to the palatal tissue surface. A single incision is thenmade to the bone through a horizontal direction approximately 2 to 3 mmapical to the gingival margin of the maxilla.

The length of the incision is determined by the size of the graftrequired to cover the proposed area, as well as depth for the elevationand removal of the donor tissue. A partial-thickness dissection is thenmade within the single incision, leaving an adequate thickness of thepalatal flap intact to minimize the chance of sloughing of the overlyingtissue; Goldstein M, et al., A critical evaluation of methods for rootcoverage. Crit Rev Oral Biol Med. 1996; 7(1):87-98.

The dissection is carried out as far apical as necessary to obtain thedesired dimensions of the graft. The connective tissue with underlyingperiosteum is then carefully dissected from the palate with theelevator. A primary closure using sutures is recommended. A freegingival graft (FGG) is harvested manually through horizontal incisionsthat are made in the two interdental papillae adjacent to the area to begrafted; Butler B L. The subepithelial connective tissue graft with avestibular releasing incision. J. Periodontol. 2003 June; 74(6):893-8;Camargo P M, et al. The use of free gingival grafts for aestheticpurposes. Periodontol 2000. 2001; 27:72-96—both incorporated herein byreference.

The incisions are made at right-angles to the gingival surface, creatinga clear butt-joint design. Two vertical apically diverging incisions arethen placed at each end of the horizontal incision and extended beyondthe mucogingival junction. Using sharp dissection of the scalpel blade,a split-thickness flap is elevated beyond the apical end of the verticalincisions, taking care that alveolar bone should not be exposed.

A FGG of 1.5 mm-1.5 cm thickness is then harvested from the hard palatefrom between the distal area of canine to the mid-palatal of firstmolar, with the dimension of the gingival graft being one and a halftimes the dimensions of the recipient area. After that, the fatty layeris removed on a side table. This requires stabilization of the graft ona wooden tongue blade or using a small instrument. The surgeon thenusually uses a small blade to shave the epithelial and fat layer.

Grafts from the donor sites can be obtained from two areas of interest:the anterior palate which has a large surface or the posterior part ofthe palate, mainly the maxillary tuberosity and lateral palate. Themaxillary tuberosity is very voluminous and thus a good site to harvestgraft tissue; Zucchelli G, et al., Patient morbidity and root coverageoutcome after subepithelial connective tissue and deep epithelializedgrafts: a comparative randomized-controlled clinical trial. J ClinPeriodontol. 2010b Aug. 1; 37(8):728-38; Zucchelli G, et al.,Predetermination of root coverage. J Periodontol. 2010a July;81(7):1019-26—both incorporated by reference. Grafts from this site areconsidered a good option for ridge augmentation while grafts from thelateral palate are good options for recession coverage. Both of thesetypes of grafts are dense and firmer than those from the anterior palateand are unlikely to undergo significant postoperative shrinkage.However, such grafts have a higher chance for necrosis than anteriorpalate.

Soft tissue grafting, using tissue harvested from palatial, oral andother soft tissue surfaces, is complicated by the variability ofthickness of freshly harvested graft-source tissue and by uneven tissuesurfaces, such as corrugated palatal surfaces.

Moreover, often a surgically desired graft thickness is only a fractionof a millimeter and this can lead to surgical errors in during manualgraft surgeries especially in soft tissue grafting. Moreover,adjustments to a tissue graft often result in wasting part of the graftand/or damaging the graft. Attempts have been made to improve graftharvesting and sizing methods such as by use of a mucotome or mucousmembrane cutter; Gunay H, et al. Harvesting technique using a mucotomeand modified surgical procedure for root coverage with enamel matrixderivatives with and without a connective tissue graft. Int JPeriodontics Restorative Dent. 2008 October; 28(5):497-507; Grant, U.S.Pat. No. 4,240,432A. Many such devices require freezing or embedding atissue and are unsuitable for preparation of slices, sections or layersof viable tissue suitable for transplanting. Microtomes require lengthyprocedures including embedding the tissue in paraffin wax or freezingthe tissue. These procedures affect the viability of the living tissueand render it non-usable for tissue grafting. Moreover, the thickness oftissue provided by microtomes, which ranges from 30-500 μm for livetissue and 10-500 μm for fixed tissue, is not suitable or practical fortissue grafting or suturing. Such prior attempts do not provide asolution for effectively splitting the graft after harvesting it.Moreover, the corrugated surface of the palate presents a challenge inachieving a uniform thickness desirable for many tissue grafts.Accordingly, these instruments still fail to overcome problems ofobtaining viable, surgically desired soft tissue grafts having asubstantially uniform thickness suitable for grafting procedures.

SUMMARY OF INVENTION

One aspect of the invention is a manual or automated tissue-graftsplitter that maximizes utilization of a harvested graft tissue andwhich provides a viable graft having a uniform thickness. The devicedoes not require that tissue be embedded prior to cutting, but can bedescribed as a free-floating cutter that splits viable tissue. Moreover,it can measure the thickness of a tissue and set a cutting location toproduce a split tissue of a desired thickness.

The tissue-splitting device or apparatus disclosed herein provides anumber of advantages to surgeons or dentists whose practices involvetissue grafting. The device quickly, easily, and accurately providesviable grafts of uniform thickness for uses in surgical procedures,especially in dental surgery. The device can be adjusted to providegrafts of different thicknesses and compared to manual procedures canprovide a standardized, viable graft of a desired thickness when used bydifferent practitioners.

Another aspect of the invention is a surgical method of grafting softtissues, especially gingival tissues, using graft sections or layers ofsoft tissue produced using the tissue graft splitter.

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A depicts an embodiment of the tissue splitter having a horizontalcutting blade 7 interposed between an upper plate 1A and lower mountingplate 6. The height of upper plate 1A is adjusted by moving theadjustable arm 1B, which supports the upper plate 1A, up or down withinheight adjuster 2 using control knob 3. The height adjuster 2,adjustable arm 1B and upper plate 1A are anchored on base 1C. A display4 is attached to the upper, external surface of plate 1A. Control knob 8controls the distance between the upper plate 1A and lower mountingplate 6, a distance which can be quantified using height scale indicator9. Lower mounting plate 6 has a rough top surface 5 for holdingharvested soft tissue in place.

FIG. 1B depicts heights h1, h2 and h3, where h2 is the thickness oforiginal tissue before cutting; h1 is the thickness of the intendedtissue to be used after cutting, and h3=h2−h1 is the thickness of theremaining tissue after cutting and removing the intended tissue.

FIG. 2 illustrates an embodiment with horizontal blade 7 positionedbetween upper plate 1 and lower mounting plate 6. The bottom surface ofupper plate 1A is equipped with three pressure sensors 15 which measurean amount of pressure imposed on a soft tissue sample sandwiched betweenthe upper plate 1 and lower rough surface 5 of the lower mounting plate6. The pressure value imposed on a soft tissue sample is measured bysensors 15 and transmitted to display 4. Thickness control knob 8 andheight scale indicator 9 are used to set the thickness of a tissuebetween rough surface 5 of the lower mounting plate and blade 7. Cuttingblade motor 11 is used to power cutting blade 7.

FIG. 3 shows a motor-side view of the tissue splitting device. Upperplate 1 and display 4 are shown along with the height adjustment 2 andupper plate height adjustment control 3. Blade/saw movement motor 12 (ormanual control 12) and blade/saw movement control knob 13 (or handle 13)move cutting blade motor 11 along horizontal blade channel 10. Heightscale indicator 9 indicates the distance between the rough surface 5 oflower mounting plate 6 and horizontal blade 7. A connection or port forcontrol cables from a microcontroller is shown at 14.

FIG. 4 shows an embodiment having a circular rotary saw blade 7positioned between the rough surface 5 of lower mounting plate 6 andupper plate having a pressure indicator display 4. The height of upperplate 1 can be adjusted using height adjustment 2 and height adjustmentcontrol 3. Thickness control knob 8 and height scale indicator 9 areused to set the thickness of a tissue between rough surface 5 of thelower mounting plate and blade 7. Horizontal blade movement channel 10and cutting blade motor 11 are shown at left.

FIG. 5 depicts a motor-side view of an embodiment having a circularrotary saw blade 7 positioned between the rough surface 5 of lowermounting plate 6 and upper plate having a pressure indicator display 4.The height of upper plate 1A can be adjusted via arm 1B using extendibleheight adjustment 2 and height adjustment control 3. Thickness controlknob 8 and height scale indicator 9 are used to set the height of theblade and thus the thickness of the resulting slices or layers of softtissue obtained by cutting harvested tissue secured between roughsurface 5 of the lower mounting plate and the upper plate 1A. Horizontalblade movement channel 10 and cutting blade motor 11 and bladehorizontal movement motor 12 and blade movement control knob or handle13 are shown in foreground. A connection or port for control cables froma microcontroller is shown at 14.

FIG. 6 provides a view of a device having a circular rotary blade 7,positioned between upper plate 1A having a pressure indicator 4 andrough surface 5 of lower plate 6, having three pressure sensors 15 onits lower, internal side. The height of upper plate 1A is adjustableusing extendible/retractable height adjustment 2 and height adjustmentcontrol 3. Horizontal blade/saw movement channel 10, cutting blade motor11, and blade horizontal motor 12 are depicted in background. Thicknesscontrol knob 8 and height scale indicator 9 are shown at left.

FIG. 7 depicts a microcontroller 16 which can be incorporated into thetissue splitting device as disclosed herein. This embodiment shows amicrocontroller with connections or wires to a control 17 for cuttingblade motor 11, connections or wires to saw horizontal movement motor18, connections or wires from the pressure sensor to the microcontroller19 and wires to a display, such as an LCD display, of pressureparameters 20.

DETAILED DESCRIPTION OF THE INVENTION

A tissue splitting device is disclosed which may be operated manually orautomatically and which securely holds harvested tissue, especially softtissue such as gingival tissue, during cutting so as to reproduciblyprovide layers of tissue having substantially uniform thicknesses. Thistissue slices or layers produced by this device are viable, ofsubstantially uniform thickness, and can be tailored using the devicefor particular surgical graft sites. Preferably the device and methodwork without requirement for embedment of the tissue during cutting andpreferably provide adjustable sample thickness.

Embodiments of this technology include, but are not limited to thefollowing.

One embodiment of the invention is a tissue splitting device comprisinga clamp comprising a horizontal and parallel upper plate and lowermounting plate, and a horizontal space between the upper plate and lowermounting plate that can accommodate a harvested tissue, wherein a bladeis horizontally positioned within the space between the upper plate andlower mounting plate and is operatively connected at one end to a blademovement channel that is horizontally aligned with the horizontal spacebetween the upper plate and lower mounting plate, wherein a top surfaceof the upper plate comprises a display operatively connected to one ormore pressure sensors on a bottom surface of the upper plate, andwherein a top surface of the lower mounting plate is a rough, frictionedsurface that prevents tissue, such as slippery soft tissue placed in theclamp from sliding.

In some embodiments, the upper and lower plates are rectangular andapproximately 10 to 30 cm long, 10 to 30 cm wide and 0.5 to 2 cm thick.The overall height of the device may range from about 5 to 20 cm. Thewidth of a space between the upper and lower plates will depend on thetype and volume of harvested tissue to be sliced or split, for example,it may range from about 0.25 to 3 cm. The dimensions of the plates canbe adjusted when needed for a particular use, such as use in conjunctionwith clinical procedures requiring a larger tissue dimensions. In apreferred embodiment, the dimensions of the plates are about 10×10 cmand the adjustable arm is about 10 cm. In some embodiments, theadjustable arm may swivel sideways for easy placement of tissue. Theother elements of the device will be proportionately sized based on thedimensions of the plates and adjustable arm.

In some embodiments, this tissue splitting or slicing device comprisesan adjustable arm attached to support base and to the upper plate whichcan be raised to increase the height of the upper plate therebyincreasing the height of the horizontal space between the upper andlower arms. The support base may be a flat, immobile surface or ananchor that firmly or immovably supports the arm and upper plate. Insome embodiments, the lower plate rests on, or is attached to, thesupport base. Typically, the lower plate is fixed, while the upper plateis movable so as to control the height of the space between the twoplates.

In other embodiments, it comprises an adjustable arm attached to theupper plate which can be raised to increase the height of the upperplate and wherein the adjustable arm is anchored to the lower mountingplate. Preferably, the lower mounting plate of the device is secured to,or rests on, a flat, immobile, horizontal surface. In some embodiments,the bottom surface of the upper plate is also a rough surface thatprevents tissue placed in the clamp from sliding so that harvestedtissue is secured both the rough surfaces of the upper and lower plates.In some embodiments, the bottom surface of the upper plate and/or thetop surface of the lower mounting plate have a coefficient of frictionon one or more tissues ranging from <0.5, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0,1.1, 1.2, 1.3 1.4, 1.5 to >1.5. In other embodiments, these surfaces mayhave a surface roughness Ra ranging from 0.5, 1, 2, 3, 4, 5, 10, 20, 50,100 or ≥500 μm to 10, 20, 50, or 100 μm.

Preferably, a coefficient of friction between the plates and the tissueis at least 0.2, 0.3, 0.4, 0.5, or 0.6 to avoid slippage of soft tissueand a preferred roughness is about 1.1, 1.2, 1.3, 1.4, or 1.5 μm ormore, when the coefficient friction is at least 0.4. Coefficients offriction and roughness may be determined by methods known in the artsuch as those described by Özin, M. C., Sümer, B., & Koç, İ. M. (2018).Estimation of Friction Force in Minimally Invasive Surgery with TactileSensors. Academic Perspective Procedia, 1(1), 959-967; Shacham et al., JBiomech Eng. August 2010, 132(8). 084502, Rashid et al., Journal of theMechanical Behavior of Biomedical Materials, Volume 14, October 2012,Pages 163-171, and Zhou, et al., (2015). Influence of surface roughnesson the friction property of textured surface. Advances in MechanicalEngineering, 7(2), 1687814014568500 which are incorporated by reference.The plates may comprise polysulfone platens (substrates) of varyingroughness between <0.12, 0.12. 0.5, 1, 2, 3, 4, 5, 6, 7 8 and >8 μm. Alow roughness of 0.12 μm may be attained by polishing. Treatment withglass beads produces a mildly rough surface (roughness=1.3 μm) while80-grit sandpaper produces a highly rough surface (roughness=8 μm). Whenlubricated human cartilage tissue was placed in contact with these threeplatens of increasing roughness, the coefficient of kinetic frictionincreased with roughness from 0.2 to 0.5 to 0.8; see Nguyen, Q. T., etal. (2010). Macroscopic assessment of cartilage shear: effects ofcounter-surface roughness, synovial fluid lubricant, and compressionoffset. Journal of Biomechanics, 43(9), 1787-1793, incorporated byreference.

In some embodiments, a nonslip surface may be produced by attaching anabrasive such as sandpaper to a surface substrate or by using a surfacesubstrate made of a polymeric material which provides control overroughness. Sandpaper increases the roughness and thus the coefficient offriction. For example, polysulfone platens (substrates) of varyingroughness are described by Nguyen et al., id. Ballotini glass beads(Potters Industry, Malvern, Pa.) were used to increase the roughness ofpolysulfone to 1.3 μm and 80-grit sandpaper was used to get a highlyrough surface (roughness=8 μm). A substrate surface comprising stainlesssteel, aluminum or another non-corrosive metal can be textured using anabrasive such as sandpaper. For example, 150-grit sandpaper increasedthe surface roughness of steel to 0.4-0.5 μm. Surface roughness can befurther increased by using lower grit sandpaper.

In some embodiments of the tissue splitting device, the splitting deviceis sterile, especially those components or surfaces that come intocontact with harvested or split tissue, such as the surfaces of upperand lower plates and the blade.

In some embodiments, the upper and lower plates, or their operativesurfaces, may be replaceable. In others the upper and lower plates andblades can be cleaned, sterilized and/or reused. Similarly, the devicemay contain a blade that can be cleaned and sterilized or can use areplaceable blade.

In some embodiments, the blade has a straight or linear edge whichextends lengthwise perpendicular to the direction of splitting orslicing a tissue. In other embodiments, the cutting blade may becircular and rotate during cutting or splitting a harvested tissue. Instill other embodiments, a thin wire or beam, such as a laser beam,which extends lengthwise perpendicular to the direction of splitting orslicing a tissue may be used to slice tissue instead of a blade.

The blade, wire, or beam may be operated and moved manually to split thetissue or by a motor to which it is operatively connected. Typically,for an automated device, the device contains a motor that moves theblade along a blade movement channel parallel to the horizontal spacebetween the upper and lower plates holding the harvested tissue. Inembodiments, where the blade, wire or beam is moved manually, the blade,wire or beam may have a handle to provide for manual movement of theblade.

The height of the blade within the space between the upper and lowerplates holding harvested tissue can be controlled by a blade heightcontrol and/or may contain a height scale indicator. In someembodiments, the height scale indicator will have visible scale markingsthat indicate the thickness of each piece of a split tissue. In otherembodiments, the height scale indicator may be linked to amicrocontroller and display which indicate the thickness of each pieceof a split harvested tissue.

As shown by FIG. 1B, the thickness knob (3) measures the total thicknessof the sample, (9) measures the height of the blade from the lowerplate. Accordingly, the thickness of both pieces of the split tissue canbe measured and calculated as shown by FIG. 1B. The lower plate uppersurface where the tissue will rest (5) is used as a reference withheight=zero. The total thickness of the original sample (h2) isdetermined by the reading on the tissue thickness control knob (3) andcan be displayed on the LCD screen. The thickness of the new sampleafter cutting is (h1) which is the height of the blade from the lowerplate surface (5). The thickness of the remaining tissue is calculatedas the difference between (h2) and (h1).

Typically, the blade height is set at a predetermined value duringsplitting or slicing of the harvested tissue to provide a slice or layeror tissue having a uniform thickness. In another embodiment, the bladeheight may be varied during cutting so as to provide a resulting sliceor layer of tissue with two or more sections having differentthicknesses or a layer of tissues with tapered ends.

The splitting device may further comprise one or more controllers ormicroprocessors operatively connected to a pressure sensor, pressuresensor display, adjustable arm, blade motor, and/or motor that moves theblade along the blade channel. Displays for each of these elements mayoptionally be connected to the element and to a microcontroller. Forexample, the microcontroller can control an amount of pressure placed onharvested tissue in the device before, during or after the tissue is cutby the blade by adjusting the height of adjustable arm 1B, adjust thehorizontal progression of the blade through the tissue, and/or thesawing speed of the cutting blade.

Another embodiment of the invention involves a method for tailoring orsplitting a soft tissue comprising harvesting a tissue sample comprisinga soft tissue, securing the harvested soft tissue between the upper andlower plates of the device as disclosed herein, setting the horizontalblade, wire or beam to a preselected position (or to one or moresequential preselected positions), and horizontally cutting the securedsoft tissue sample, and recovering a slice of the soft tissue having thepreselected thickness. There is no need to freeze, fix, or embed aharvested tissue in embedding agent like wax or resin. A harvestedtissue sample is kept viable and free during the splitting or cuttingprocess.

In another embodiment, a harvested tissue may be sliced two, three ormore times to provide several slices or layers of uniform or preselectedthickness. These multiple layers may be taken from the top or bottom ofa harvested tissue or from the center of a harvested tissue securedbetween the upper and lower plates.

Once a layer or slice of tissue is split or sliced from the harvestedtissue, it may be removed from the device, washed with a sterile saline,antibiotic-containing, or a nutritive medium, and, if necessary, haveits dimensions, such as length and width, further tailored to fit aparticular graft site. A layer or slice of tissue may be retained orrefrigerated prior to use as a graft, for example, at a temperatureabout 0, 10, 20, 25, 30 to 37° C.

In some embodiments the soft tissue that is split is connective tissue,keratinized gingival tissue, non-keratinized gingival tissue, a softtissue comprising a mucous membrane, epithelium, or endothelial orcardiac tissue. Keratinized gingival tissue derives from keratinizedgingiva which is the part of the oral mucosa which covers the gingivaand hard palate. It extends from the free gingival margin to themucogingival junction and consists of the free gingiva as well as theattached gingiva. It can be transplanted to restore defects or areas ofrecession or degeneration in keratinized gingiva. Non-keratinizedgingival tissue derives from alveolar mucosa which is non keratinizedoral epithelium and is located apical to the keratinized tissue,delineated by the mucogingival junction (MGJ). Such mucosa can surrounda healthy tooth and thus when transplanted may be used to replace orrestore tissue around a tooth.

Preferably, the splitting device as disclosed herein is oriented asshown in the figures with the lower plate supported by or fixed tohorizontal surface with the blade cutting the tissue between the upperand lower plates horizontally, end-to-end. In other embodiments, theentire device may be rotated so that the blade cuts the tissuevertically upward or vertically downward or at an angle.

Another embodiment of the invention is a method for performing a softtissue transplant comprising surgically removing a soft tissue from asubject, splitting the soft tissue in the splitting device as disclosedherein under conditions that provide a layer of viable soft tissue ofuniform or preselected thickness (or thicknesses), and transplanting thelayer of tissue into a graft site on a subject. In some embodiments,this method uses a soft tissue that is gingival or connective tissue andprovides layers of uniform thickness for transplantation into the mountof a subject who is in need of a connective tissue or free gingivaltissue.

Soft tissue. The term soft tissue refers to tissues that connect,support, or surround other structures and organs of the body, not beingbone. Soft tissue includes tendons, ligaments, fascia, skin, fibroustissues, fat, and synovial membranes, and muscles, nerves and bloodvessels. All tissues found within the body that are not those of bonesor certain organs are considered soft tissues. In some embodiments, thecomposition of soft tissue comprises mainly of elastin and collagen andit may comprise fibroblasts, chondroblasts or other cells that produceelastin or collagen. Ground substance, non-cellular, fibrous componentsof a cell, also can make up part of a soft tissue.

Many soft tissues are hyperelastic materials, which have a nonlinearstress-strain curve, and have the potential to undergo largedeformations and still return to the initial configuration whenunloaded. A soft tissue may be viscoelastic, incompressible oranisotropic. Some viscoelastic properties observable in some softtissues are relaxation, creep and hysteresis. Mechanical properties ofsoft tissues may be measured using various methods includinghyperelastic macroscopic models based on strain energy, mathematicalfits where nonlinear constitutive equations are used, and structurallybased models where the response of a linear elastic material is modifiedby its geometric characteristics.

Other tissues that may be split using the device disclosed herein softtissues such as skin layers, mucus membrane, connective tissue,epithelium, cardiac tissue, keratinized gingival, non-keratinized,gingival, para-keratinized, gingival, cartilage, cornea, periosteum,muscles, vessels, artery, membrane and barrier tissue.

The porcine soft tissue system is representative of the human system interms of tissue mechanics; Shacham et al., supra. The liver is among the‘softer’ soft tissues in the body and can help decide a reasonablecompressive stress/pressure limit to prevent tissue damage in theexperiments. Based on a study by Chen et al., the porcine liver startsshowing significant changes in microarchitecture, such as an increase inthe density of fissure cracks, within 30% compressive strain. Looking atthe stress-strain curve for this tissue, keeping the pressure under 30kPa is important to prevent tissue damage. Since the liver is softerthan most other soft tissues, this threshold should work for othertissues too.

Moreover, biomechanical engineering studies may be conducted for eachtissue by the end-user to measure tissue pressure injury tolerance andbiomechanics of oral mucosa. The results can them be fed into themicroprocessor to determine the safe pressure parameters and the usercan choose which the tissue and preset pressures will be utilized.However, manual override for the pressure can be done by the user byselecting a value in bar or pascal.

Soft tissue grafts that may be produced using the device as disclosedherein include gum tissue grafts such as connective tissue grafts andfree gingival grafts. Connective tissue grafting is a common method usedto treat root exposure. During the procedure, a flap of skin is cut atthe roof of the mouth (palate) and tissue from under the flap, calledsubepithelial connective tissue, is removed and then stitched to the gumtissue surrounding the exposed root. After the connective tissue formingthe graft has been removed from under the palatal flap, the flap isstitched back down. A free gingival graft is similar to aconnective-tissue graft and involves the use of tissue from the roof ofthe mouth. However, instead of making a flap and removing tissue underthe top layer of flesh, a small amount of tissue is removed directlyfrom the roof of the mouth and then attached to the gum area beingtreated. This method is used most often in people who have thin gums tobegin with and need additional tissue to enlarge the gums. For eithertype of graft, the harvested tissue may be sliced to a uniform thicknessor may otherwise be tailored as disclosed herein. A tissue or layer ofsplit or sliced tissue having a substantially uniform thickness may varyin average thickness over its length by 1, 2, 5, 10, 15 or 20%.Preferably uniformity of the thickness should be within ±0.02, 0.03,0.04, 0.05, 0.06, 0.07, 0.08, 0.09, or 0.1 mm.

Preferably, the device and splitting method as disclosed herein isconfigured to use, or involves soft tissue samples. However, in someembodiments, tissues other than soft tissues may be used, such as boneor a tissue of an organ, or tissue that is a mixture of soft andnon-soft tissues. The device and method herein may be used to slicetissue harvested in vivo or ex vivo, tissue from a living or deceaseddonor, tissue from a tissue bank, tissues grown in vitro, or artificialtissue or biomaterials.

Surgical blades. The thickness and type of blade is typically selectedbased on the type of harvested tissue, the type of graft being made andthe intended usage of the resulting sliced tissue. In some embodiments,the device uses a sharp steel, carbon-steel, glass, ceramic, sapphire,or diamond blade. A blade with a straight edge or a toothed blade may beselected depending on the type of harvested tissue and the thickness ofthe sliced layer to be cut. In some embodiments, a blade will have anantifriction coating, such as, but not limited to, platinum orpolytetrafluoroethylene (PTFE) in preferred embodiments, the blade willact as a saw with back and forth motion or vibration for a linear bladeand rotary motion for a circular blade. An interchangeable blade edgetype is selected depending on the type of tissue.

Pressure sensors. Typically, thin or ultrathin compressive or shearstress sensors are attached to, or embedded in the bottom surface of theupper plate, so as to measure compressive force of the upper and lowerplates on the tissue, or shear forces applied by the blade on a tissuesample secured between the upper and lower plates. These includeultrathin, embeddable sensors such as those described by hypertexttransfer protocolsecure://www.tekscan.com/products-solutions/embedded-force-sensors(incorporated by reference, last accessed Apr. 15, 2020). A pressuresensor may be configured to monitor compressive pressure or stressapplied on a sample prior to or during splitting as well as a rate ofchange of compressive stress or pressure during handling or splitting.In some embodiments a sensor will detect and measure compressive stressbetween 0, 100, 200, 300, 400 or 500 psi. Such pressure sensors preventcrushing of a harvested tissue placed in the device by keeping pressurewith a suitable range for a particular type of tissue. The pressuresensors can also be used to control pressure imposed on the harvestedtissue to help stabilize it during cutting, or to flatten a tissue to auniform thickness for splitting or cutting with the blade. Pressuresensors are preferably operably connected to a control for theadjustable arm and to a microcontroller that can maintain pressurewithin a preselected range by adjusting the height of the upper plateand which can display pressure values or harvested tissue thicknessprior to and during cutting.

In some embodiments, in addition to compression pressure sensors, one ormore sensors that measure mechanical resistance during cutting of aharvested tissue may be operatively connected to the cutting blade andhorizontal movement motor. These can, for example, measure resistanceimposed against the advancing cutting blade when a harvested tissuecontains tissues of different densities. If desired, a microcontrolleror circuit breaker mechanism may be used to auto-stop the blade when achange in mechanical resistance is detected which may indicate contactof the cutting blade with a material having a different or unexpecteddensity.

Piezoelectric pressure sensors are well-suited to measure pressure inthe near 30 kPa range as well as measuring mid-range pressures (100-108Pa) and are incorporated by reference to Ripka, P., & Tipek, A. (Eds.).(2007). Modern sensors handbook (pp. 978-1). London, UK: ISTE. Thesesensors work on the principle of piezoelectricity, whereby the pressuresignals are converted to electric signals in the form of voltagechanges. They are less expensive, compact, and allow for dynamicpressure measurements with a response time on the order of amillisecond. Specifications for commercially available piezoelectricpressure sensors are incorporated by reference and include 0.7 kPa to 70Mpa (worldwideweb.avnet.com/wps/portal/abacus/solutions/technologies/sensors/pressure-sensors/core-technologies/piezoelectric/);and 0-108 Pa (worldwideweb.bdsensors.de/en/pressure/piezoelectric-pressure-sensors/). Each ofthe above last accessed Jul. 27, 2020.

A 5 N load cell, which can measure forces as low as 20 mN, which iswithin the limits of what soft tissues are capable of handling can alsobe used and are incorporated by reference to Comley, K., & Fleck, N.(2012). The compressive response of porcine adipose tissue from low tohigh strain rate. International Journal of Impact Engineering, 46, 1-10.There are also 100 N load cells that have a resolution of 5 mN; Chen etal., supra. These can also be used to measure stresses (pressure) in therealm of soft tissue mechanics. A load cell can be placed under thelower substrate and force measured by it can be converted into pressuredepending on the area of the sample.

Sensors will measure both compressive pressure and stress and strainforces. The stress and strain forces (measured from the plates) incombination with the compressive pressure data as well as blade movementsensor data, will control the splitting action to avoid losing theviability of the tissue while maintaining the cutting efficiency.

Moreover, an autostop feature will be implemented through the softwareof the microprocessor whereby it will sense the amount of current drawnby the blade motor. If there is a change in the amount of current beingdrawn this will mean that the blade is cutting into a different tissue(different tissue density) and immediately the blade will be stopped

Non-slip surface. A non-slip, frictioned surface helps hold a harvestedtissue on the bottom plate of the splitting device described herein.This surface may be imprinted with, or constitute a grating comprising araised pattern of dots, ridges or other designs to provide a nonslipsurface. Alternatively the top surface of the bottom plate may betreated with a commercially available non-slip coating, such as anonslip or antislip paint or polymer (e.g. urethane or rubber) coating.In some embodiments, either or both of the bottom surface of the topplate and/or the top surface of the bottom plate may comprise nonslip orantislip surface. In some embodiments, the nonslip surface may have araised edge at one or both ends or a depression into which a base of theharvested tissue may be placed to help secure the tissue duringsplitting.

Controller. Sensors are operative connected to a controller, such as amicroprocessor, that processes sensor input and outputs a pressure valueon a display which is preferably attached to the top of the upper plate.In some embodiments, the controller may be operatively connected to acontrol that adjusts the splitting or rotational speed of the blade, toa control that adjusts the speed of blade along a blade movement channelthrough the tissue to modulate shear force on the tissue or to a controlwhich adjusts the position of the upper plate so as to modulate thecompressive pressure on the tissue. According to some embodiments, thecontroller can comprise one or more types of processors and/orelectronic circuitry that can implement one or more computer and/ormachine readable, writable, and/or executable components and/orinstructions that can be stored in a memory. For example, the controllercan perform various operations that can be specified by a computerand/or machine readable, writable, and/or executable components and/orinstructions including, but not limited to, logic, control, input/output(I/O), arithmetic, and/or the like. In some embodiments, controller cancomprise one or more central processing unit, multi-core processor,microprocessor, dual microprocessors, microcontroller, System on a Chip(SOC), array processor, vector processor, and/or another type ofprocessor.

Thickness of slices. Tissue slices may range in thickness from about 0.1(100 microns), 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6,7, 8, 9, 10 or >10 mm or any intermediate value or subrange within thisrange. A desired slice thickness may be set using a thickness controlknob to adjust blade height and/or by adjusting the height of the armsupporting the upper plate.

Pressure range. An amount of pressure applied on a tissue placed betweenthe upper and lower plates of the device disclosed herein is selected soas to minimize damage to the tissue while securing it in the device soit can be uniformly sliced along its length. Preferably the amount ofcompressive force or shear pressure applied to the tissue duringsplitting does not decrease the viability of a graft made using thesliced tissue by more than 1, 2, 5, 10, 20, 30, 40 or 50% compared to agraft made using an originally harvested tissue or tissue slicesprepared without mechanical application of compressive force. Pressureapplied may preferably range from 50, 60, 70, 80, 90, 100, 110, 120,120, 130, 140, 150 to 200 psi.

Typically, a compression range should be under 30 kPa to be safe inorder to prevent tissue damage. Since information on human soft tissuedamage mechanics is sparse, we will have to rely on the porcine system,which is considered to be quite representative of the human system interms of tissue mechanics (Shacham et al., supra). Liver is among the‘softer’ soft tissues in the body and can help decide a reasonablecompressive stress/pressure limit to prevent tissue damage in theexperiments. BasPorcine liver starts showing significant changes inmicroarchitecture, such as an increase in the density of fissure cracks,within 30% compressive strain; see Chen, J., et al. (2018). Quantitativeanalysis of tissue damage evolution in porcine liver with interruptedmechanical testing under tension, compression, and shear. Journal ofBiomechanical Engineering, 140(7); Miller, et al. (2005). Method oftesting very soft biological tissues in compression. Journal ofbiomechanics, 38(1), 153-158; and, Miller et al, (2002). Mechanicalproperties of brain tissue in tension. Journal of Biomechanics, 35(4),483-490, and Bilston, L. E., et al. (2001). Large strain behaviour ofbrain tissue in shear: some experimental data and differentialconstitutive model. Biorheology, 38(4), 335-345, each incorporated byreference.

Looking at the stress-strain curve for this tissue, keeping the pressureunder 30 kPa is important to prevent tissue damage. Since liver issofter than most other soft tissues, this threshold should work forother tissues too.

As shown in FIGS. 1A to 6, the device comprises a lower mounting plate 6on which harvested tissue is placed for later splitting. It has anon-smooth or rough surface 5 to help harvested tissue to stay in placeand not slip during splitting.

An upper plate 1A is lowered onto the tissue to keep it in place as wellas keep its surface uniform. The upper plate height is controlledmanually, electrically, electronically or by any other means using thetissue thickness control knob 3. The height control mechanism is housedin the upper plate height-adjustment cylinder 2.

A pressure sensor 15 measures the pressure exerted by the upper plate 1on the tissue and displays this pressure on the LCD screen 4. The userwill exert the predetermined amount of pressure on the tissue sample sothat it stays in place but does not exceed the pressure limit so as notto damage the tissue. A cutting device 7 which can be a horizontal bladeshown in FIGS. 1, 2, 3, or a rotating disc as shown in FIGS. 4, 5, 6 orany other cutting mechanism, such as laser, a fine wire, is held by anarm 10 attached to the lower plate and can move in the horizontal blademovement channel 10 parallel to the length of the tissue sample betweenthe plates.

The thickness of the tissue to be produced is determined by setting acutting blade height which can be controlled manually, electrically,electronically or by any other means using the tissue thickness controlknob 8. To provide a uniform and standardized thickness of a tissueslice or layer, this control knob may be calibrated to move inincrements, for example in 0.1, 0.2, 0.3, 0.4, or 0.5 mm increments. Aheight scale indicator 9 is used to determine or quantify the thicknessof the slice or layer of tissue removed from the harvested tissue.

The horizontal movement motor 12 is controlled by the cutting blademovement control 13 which may be operably connected to amicrocontroller. The sawing speed of a blade may be controlled viacutting blade motor 11 which may be operably connected to amicrocontroller.

The control of the electronics and electrical devices comes from amicrocontroller 16 in FIG. 7 which is interconnected by wire 17 from themicrocontroller to control the cutting or sawing motor 11, wire 18 tocontrol horizontal movement motor 12, which controls the movement of theblade through the harvested tissue, cables 19 from the pressure sensor15 and by wires 20 wires from the microcontroller to the LCD display 4which conveniently displays the pressure exerted on the tissue samplewhen the upper compression plate 1A is lowered.

The device as disclosed herein may be made of various materialsincluding metal, hard plastics or polymers, wood, ceramics orcombinations thereof.

Terminology. Terminology used herein is for the purpose of describingparticular embodiments only and is not intended to be limiting of theinvention.

As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed items and may beabbreviated as “/”.

Any numerical range recited herein is intended to include all sub-rangesand values subsumed therein.

Spatially relative terms, such as “under”, “below”, “lower”, “over”,“upper”, “in front of” or “behind” and the like, may be used herein forease of description to describe one element or feature's relationship toanother element(s) or feature(s) as illustrated in the figures. It willbe understood that the spatially relative terms are intended toencompass different orientations of the device in use or operation inaddition to the orientation depicted in the figures. For example, if adevice in the figures is inverted, elements described as “under” or“beneath” other elements or features would then be oriented “over” theother elements or features. Thus, the exemplary term “under” canencompass both an orientation of over and under. The device may beotherwise oriented (rotated 90 degrees, 180 degrees, or at otherorientations) and the spatially relative descriptors used hereininterpreted accordingly. Similarly, the terms “upper”, “lower”,“horizontal space”, “height”, “upwardly”, “downwardly”, “vertical”,“horizontal” and the like are used herein for the purpose of explanationonly unless specifically indicated otherwise. The citation of referencesherein does not constitute an admission that those references are priorart or have any relevance to the patentability of the technologydisclosed herein. Any discussion of the content of references cited isintended merely to provide a general summary of assertions made by theauthors of the references, and does not constitute an admission as tothe accuracy of the content of such references.

1. A tissue splitting device comprising: a clamp comprising an upperplate and lower mounting plate, wherein the upper plate and lowermounting plate are parallel with one another and define a horizontalspace between and parallel to the upper plate and lower mounting platethat can accommodate a harvested tissue, wherein the clamp comprises anadjustable arm attached to a support base and to the upper plate whichis configured to adjust the vertical position of the upper plate therebyadjusting the height of the horizontal space between the upper plate andlower mounting plate, wherein the top surface of the upper platecomprises a display operatively connected to one or more pressuresensors on a bottom surface of the upper plate, wherein a top surface ofthe lower mounting plate is a rough, frictioned surface having a surfaceroughness Ra of at least 1 μm that prevents tissue placed in the clampfrom sliding, a saw-toothed blade positioned within the space betweenand parallel the upper plate and lower mounting plate, a blade movementchannel to which one end of the saw-toothed blade is operativelyattached, wherein the blade movement channel is longitudinally alignedwith the horizontal space between the upper plate and the lower mountingplate and which, during operation of the device, permits forwardmovement of the saw-toothed blade from one end of the horizontal spaceto the other end of the horizontal space.
 2. (canceled)
 3. The tissuesplitting device of claim 1, further comprising a handle that isoperatively connected to the saw-toothed blade and can manually move thesaw-toothed blade forward along the saw-toothed blade movement channel.4. The tissue splitting device of claim 1, further comprising athickness control which moves the saw-toothed blade upward or downwardin the horizontal space between the upper plate and lower mounting plateand a height scale indicator describing the height of the saw-toothedblade.
 5. (canceled)
 6. The tissue splitting device of claim 1, whereinthe bottom surface of the upper plate has a surface roughness, Ra, ofgreater than 1 μm. 7-12. (canceled)
 13. The tissue splitting device ofclaim 4, further comprising a microcontroller that is operativelyconnected to the thickness control so as to control the height of thesaw-toothed blade and, optionally, connected to a display whichindicates the thickness of split tissue produced by splitting tissuebetween the upper and lower plates. 14-20. (canceled)